Micro size gutter (4m), typically for a shed. (College Town GU47)

Hello, I'm looking for a narrow gutter, not for water, but for attaching to band library shelves to put sheet music parts in temporarily for sorting before filing (the music will lean against the box files already there).

If you think the presumably-used guttering can be cleaned up enough for this purpose I would be grateful to collect it and clean it if not too far out of my driving routes.
Happy freegling